Typically, a constant velocity universal joint has inner and outer spherical races coupled together by a series of balls engaging generally parallel grooves in the races. It is important that the speed of rotation of the two races remains always the same, whatever the angular adjustment of the axes of the two races. This depends on maintaining the plane of the balls so as to bisect the angle of adjustment. At present, this is accomplished by placing a spherical cage between the races, slotted to hold the balls. However, the provision of a cage increases cost, adds an additional part, and generates excess heat in operation.